1. Field of the Invention
The present invention relates to assemblies for inhibiting wind erosion and, more particularly, such an assembly that can be installed as part of a green roof system.
2. Description of the Related Art
Various materials are known which can be placed over a ground surface to inhibit wind erosion and/or other forms of erosion. Typically, such erosion mats are formed of fabric or film materials that can be commercially obtained on relatively large rolls. During installation, the erosion mat is unrolled onto the ground surface to be protected and then secured in place. When such erosion mats are installed on a natural ground surface, spikes or similar anchoring devices can be driven through the erosion mat from above into the ground to thereby hold the material in place on the ground surface.
Such erosion mats are also employed with green roof systems. A variety of green roof systems are known in the art. For example, modular green roof systems are described in U.S. Pat. Nos. 6,178,690 B1 (Yoshida et al.); 6,237,285 B1 (Yoshida et al.); and 6,711,851 B2 (Mischo) the disclosures of which are expressly incorporated herein by reference. Non-modular green roof systems are also known and can be used to economically cover large rooftop expanses. In such non-modular systems, it is typical to install a drainage layer on the roof structure in the area of the green roof system. A filter fabric is then placed over the drainage layer and an engineered soil or other plant growing medium is installed over the filter fabric. It is also often necessary to install a wind erosion mat to cover the upper surface of the soil layer. The need for a wind erosion mat can be particularly acute for a green roof system installed on a tall building in an urban area where the system will be subjected to high winds and it is desirable to prevent debris, such as small stones, from falling from the roof.
In a conventional non-modular green roof system, the depth and consistency of the soil layer will generally not be sufficient to secure an erosion mat in the same manner as in the soil of a natural ground surface. Moreover, the use of spikes or similar anchoring mechanisms in a green roof system can potentially damage the underlying roof structure and water barriers if the spikes are driven to far into the soil layer. Instead, it is typical for an additional layer of felt, a moisture retention fabric or other similar material to be laid down directly on top of the filter fabric to facilitate the attachment of the erosion mat. At spaced intervals where it is desired to secure the erosion mat, two small spaced apart slits are cut into the felt layer. A zip tie (such as those commonly used when securing electrical wires), a short length of wire, a twist tie or similar fastening device is manually threaded through the slits at each spaced interval. The soil layer is then placed over the felt and filter fabric layers. The zip ties must then be relocated and positioned so that they extend above the upper surface of the soil layer. The erosion mat is then unrolled over the soil layer and the two projecting ends of each of the zip ties must be manually threaded through the erosion mat at spaced apart locations and secured together to thereby fasten the erosion mat to the felt layer.
While effective, this method of installing an erosion mat in a green roof system is very labor intensive and, as a result, can be quite expensive.